With the development of broadband networks, mobile communication is no longer limited to traditional voice communication. Multimedia service in conjunction with various media types, such as audio, video, picture, and text, will continue to be developed. With the combination of data services, such as Presence (Presence service), Short Messages, WEB browsing, location information, PUSH (push service), file sharing and the multimedia services, various requirements from users may be met. The multimedia services include:
1) Message Services: instant messages, chat rooms and multimedia short messages;
2) Video Services: entertainments, multimedia information exchange and daily intercommunion;
3) Electronic Commerce: product directories, search engines, shopping service, order management and payment;
4) Games: single-player games and group games;
5) Location Services: Seeking the Missing, Guide and Alarm; and
6) Personal Assistants: address books, schedules, bookmark management, file storages, events reminder and E-mail.
With the promotion of various multimedia applications, a standard organization of 3rd Generation Partnership Project (3GPP) puts forward an Internet Protocol (IP)-based IP Multimedia Subsystem (IMS) architecture, which aims to realize various multimedia applications in a communication network by using a standardized open structure and provide with users more choices and more abundant experiences.
Session Initiation Protocol (SIP) was developed in the middle of 1990s. The SIP may be used for controlling the stream transmission of audio/video contents on a Web. SIP messages are based on text to be easily read, debugged and programmed, and thus more intuitively to designers.
Similar to an E-mail client, SIP re-uses the type of Multipurpose Internet Mail Extension (MIME) description and a plurality of existing mature Internet services and protocols, such as Domain Name System (DNS), Real Time Transport Protocol (RTP), and Resource Reservation Protocol (RSVP). Therefore, all session-related applications may initiate automatically without any new service to support SIP infrastructure.
SIP is independent of the Transmission Layer, and the underlay transmission of SIP may employ IP over Asynchronous Transmission Mode (ATM). Users independent of the underlay infrastructure may be flexibly connected by SIP using User Datagram Protocol (UDP) and Transmission Control Protocol (TCP).
SIP supports multi-device function adjustment and negotiation. If a service or a session initiates videos and voices, the voices may be transmitted to a device that does not support videos; other device functions, such as one-way video stream transmission function may also be used.
With the developments of network technologies, multi-party communication has becomes a prevalent service. In order to realize multi-party communication, a concentrated control point is required to manage the multi-party communication, thereby the consistency and real-time characteristic of the management may be guaranteed. For example, when a user applies for sending an audio service, the system, such as a Push-to-talk Over Cellular (PoC) system and a Conference (a server providing a function of user states) system, needs one control point, and only one control point, for judgment.
A PoC system is a central-controlled multi-party multimedia communication system, which is a Push-To-Talk (PTT) service realized on a cellular system as defined by Open Mobile Alliance (OMA). The concept of the PoC service comes from interphones. The usage mode of the PoC service experienced by users is similar to that of the interphone. The PoC service may realize simple and shortcut half-duplex communication manner. By pre-configuring a communication group, a user may deliver the voice to all the other members in the group during communication simply by pushing a specific button, without dialing the number. The push-to-talk, calling and call connecting are accomplished instantly, and the receiving party may hear the voice without any responsive operations. The communication process of the PoC service employs half-duplex mode, in which when one party is speaking, other members can only listen to the speaker without speaking.
The OMA is responsible for drawing up the PoC standard specifications, in which the defined network structural diagram of the PoC specification is shown in FIG. 1, which includes the following primary entities:
1) a PoC Server, serving as a primary call control device for the PoC service and an Application Server in IMS network;
2) a PoC XDMS, serving as a server for storing data, such as group information required by the PoC services;
3) a PoC Client, serving as a PoC Client, the PoC Client together with the PoC Server adapted to initiate and receive a PoC call, request a floor, and make a speech.
The PoC service is a half-duplex voice and multimedia communication system. After a PoC group call is established, the user may apply to the PoC Server for the floor via Talk Burst Control Protocol (TBCP). The user may only be allowed to speak upon obtaining the floor, and thereby the media stream sent by the speaking may be forwarded to other members of the group by the PoC Server.
POC2.0 is a higher version of the PoC service that is being drawn up by OMA at present, and it is an extension and upgrade of the service defined in POC1.0. POC2.0 allows a user to establish a multimedia session for instant communication with other one or more users via a specific button, and allows the user to deliver various media types during the session, such as static pictures, real-time video streams, file transmission and texts. POC2.0 is back compatible to POC1.0, and also supports the half-duplex voice service in POC1.0.
The PoC service information includes:
1) user setting messages, such as PoC service settings, PoC access control settings and CPM user settings;
2) system setting messages, such as Operator's policies;
3) indication messages in signaling messages, such as response mode, access priority and order and Media Burst Control Scheme (MBC Scheme);
4) indication messages in media control messages, such as version indication in a TBCP or MBCP message;
5) service information saved in the network system, such as MBC Scheme in the group information;
6) user subscription information, such as access criteria of a service used by a user.
The network operation for the PoC service is usually determined according to various information, such as the above user setting messages, indication of the signaling plane message, indication of the user plane message (media control message), the user subscription messages, service information saved in the network system and Operator's policies. With the development of the PoC service, there will be more and more messages, such as the above user setting messages, service information saved in the network system, Operator's policies.
At present, in the above service information, except that part of the Operator's policies may be configured mutual exclusively, there exists no method for correlative processing among user setting messages, among the indication information in signaling messages, among the indication information in media control information, among service messages saved in the network system, and among user subscription information.